Mathew m



M. M. KERR.

DENTAL INSTRUMENT.

APPLICATION FILED APH. 24. 1915.

1,307,446. v n Patented June 24, i919.

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jm W7 l mmm IINITED STATES PATENT OFFICE.

MATHEW M. KEER, OF DETROIT, MICHIGAN, ASSIGNOR TO DETROIT DENTAL MANU- FACTURING COMPANY, OF DETROIT, MICHIGAN, A CORPORATION OF MICHIGAN.

DENTAL INSTRUMENT.

Specication of Letters Patent.

Patented J une 24, 1919.

To all whom t may concern.'

Be it known that I, MA'rHEw M. KERR, a citizen of the United States of America, residing at Detroit, in the county of lVayne and State of Michigan, have invented certain new .and useful Improvements in Dental Instruments, of which the following is a specification, reference being` had therein to the accompanying drawings.

The invention relates to dental tools which are designed for use in clearing out the nerve canals in devitalized teeth. Such instruments are usually in the form of reamers which are sufficiently flexible to follow the curves of the canals and operate by a rotary movement in said canals.

It is the object of the present invention to form a broach which, instead of operating as a reamer, may be used as a file, performing its work when longitudinally reciprocated.

In the drawings:

Figure 1 is a magnified elevation of the broach;

Figs. 2 and 3 are cross sections on line and y-y Fig. l; and

Fig. 4 is a longitudinal section.

In the present state of the art dental tools of thischaracter are usually formed of fine steel rods or needles, which are ground into a polygonal and pointed form and are then twisted to give a slightly spiral form to the cutting edge. The pitch of the spiral is, however, such that the general direction is longitudinal of the needle, and, as before stated, in operation the tool must be rotated to perform its work. In my improved construction, the polygonal rod is twisted to such an extent, or otherwise so fashioned, that the cutting edge extends transverse to the longitudinal axis, and at such an angle that the work will be performed by a longitudinal reciprocating movement instead of a rotary movement.

As specifically shown, A is the round rod, which is ground with polygonal faces B forming cutting angles C. These angles or cutting edges, when the rod is twisted, will form spirals D of relatively flat pitch, while at the point the cutting edges extend longitudinally, as at E, to form a reamer.

In use, the tool when inserted in a nerve canal is moved longitudinally, causing the transverse cutting edges D to operate as files. This instrument is particularly useful where the canal is not round in cross section, as the cut is not produced by a rotary motion.

The cutting edges are preferably formed with a sharper angle on the upper side than that upon the lower side, so that the cutting will be effected on the outward pull instead of upon the inward push of the instrument.

This is advantageous, as the small size and' flexibility of the rod would endanger breaking if the work were performed by a pushing movement.

Ihat I claim as my invention is l. A dental instrument comprising a rod provided with ground polygonal faces forming cutting edges, said rod having the cutting edges at one en-d tapering to a point and extending substantially longitudinally thereof, and said rod being twisted to form spirals of relatively flat pitch, the cutting edges of the spirals having a sharper angle on the side opposite the point than the cutting edges on the same side with the point.

2. A dental instrument, comprising a polygonal rod twisted to form a spiral cutting ,edge at an angle to effect cutting when moved longitudinally of the axis of the rod.

3. A dental instrument, comprising a rod having a spirally twisted cutting edge, the pitch of the spiral being such as to effect a cutting operation when reciprooated longitudinally of the axis of the rod.

4. A dental instrument, having a point portion with longitudinally-extending cutting edges and a portion having a spirallytwisted cutting edge, the pitch of the spiral being such as to effect a cutting operation when reciprocated longitudinally of the axis of the rod.

In testimony whereof I affix my signature in presence of two witnesses.

MATHEW M. KERR.

Witnesses EDWIN HERZOG, K. CARLYLE.

Copies of this patent may be obtained for ve cents each, by addressing the- Commissioner of Patents. Washington, I). C. 

